Method and apparatus for controlling buoyancy

ABSTRACT

1. A device for controlling the depth at which an object will float comprising: A FLOTATION CHAMBER HAVING A CENTRAL OPENING IN ITS UPPER SURFACE AND AN OPEN BOTTOM; A PRESSURE SOURCE IN SAID CHAMBER; SAID PRESSURE SOURCE INCLUDING A DIAPHRAGM WHICH IS EXPOSED TO THE FLUID IN WHICH THE DEVICE IS FLOATED; MEANS DEFINING A PASSAGE BETWEEN THE INTERIOR OF SAID CHAMBER AND SAID CENTRAL OPENING; GUIDE MEANS ATTACHED TO SAID UPPER SURFACE ABOUT SAID CENTRAL OPENING; SAID GUIDE MEANS EXTENDING TRANSVERSELY THROUGH SAID CHAMBER; THE INTERIOR END OF SAID PASSAGE DEFINING MEANS MOVABLY MOUNTED ON SAID GUIDE MEANS; A GAS SUPPLY IN SAID CHAMBER AND MEANS ASSOCIATED THEREWITH FOR DISPENSING SAID GAS INTO SAID CHAMBER TO PROVIDE INCREASED BUOYANCY WHEN THE FLUID IN SAID CHAMBER REACHES A PREDETERMINED LEVEL; AND NON-EXTENSIBLE MEANS CONNECTING THE INTERIOR END OF SAID PASSAGE DEFINING MEANS AND SAID DIAPHRAGM; SAID PASSAGE DEFINING MEANS DEFINING A DECREASED AIR SPACE IN SAID CHAMBER AND RELEASING AIR THEREFROM WHEN SAID DEVICE IS AT DEPTHS LESS THAN A PREDETERMINED DEPTH; SAID PASSAGE DEFINING MEANS DEFINING AN INCREASED AIR SPACE IN SAID CHAMBER WHEN SAID DEVICE IS AT DEPTHS GREATER THAN A PREDETERMINED DEPTH; SAID DISPENSING MEANS ACTUABLE TO RELEASE GAS INTO THE INCREASED AIR SPACE WHEN THE FLUID IN SAID CHAMBER IS ABOVE A PREDETERMINED LEVEL.

United States Patent Kamalian 51 Sept. 19, 1972 [54] METHOD AND APPARATUS FOR CONTROLLING BUOYANCY [72] Inventor: Neubar Kamalian, West Los Angeles, Calif.

[73] Assignee: The United States of America as represented by the Secretary of the Navy [22] Filed: May 28, 1964 [21] Appl. No.: 371,141

[52] US. Cl. ..102/14 [51] Int. Cl ..F42b 22/08 [58] Field of Search ..102/10, 13, 14,7; 114/25; 9/8

[56] References Cited UNITED STATES PATENTS 1,120,621 12/1914 Lindmark ..102/14 1,379,273 5/1921 Feiler ..89/l.7 B

3,015,271 1/1962 MacAdams 102/14 3,158,062 11/1964 Feiler ..89/1.7 B

FOREIGN PATENTS OR APPLICATIONS 78,785 12/1917 Germany Primary Examiner-Verlin R. Pendegrass AttorneyGeorge J. Rubens, Q. Baxter Warner and C. E. Vautrain, Jr.

EXEMPLARY CLAIM l. A device for controlling the depth at which an object will float comprising:

a flotation chamber having a central opening in its upper surface and an open bottom;

a pressure source in said chamber;

said pressure source including a diaphragm which is exposed to the fluid in which the device is floated;

means defining a passage between the interior of said chamber and said central opening;

guide means attached to said upper surface about said central opening;

said guide means extending transversely through said chamber;

the interior end of said passage defining means movably mounted on said guide means;

a gas supply in said chamber and means associated therewith for dispensing said gas into said chamber to provide increased buoyancy when the fluid in said chamber reaches a predetermined level; and

non-extensible means connecting the interior end of said passage defining means and said diaphragm;

said passage defining means defining a decreased air space in said chamber and releasing air therefrom when said device is at depths less than a predetermined depth;

said passage defining means defining an increased air space in said chamber when said device is at depths greater than a predetermined depth;

said dispensing means actuable to release gas into the increased air space when the fluid in said chamber is above a predetermined level.

9 Claims, 3 Drawing Figures PATENIEMEP 19 1912 IAVENTOR. NEUBAR KAMALIAN BY 65 ,AGE/VT ZJ-u/ METHOD AND APPARATUS FOR CONTROLLING BUOYANCY The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

The present invention relates in general to methods and devices for controlling the level of dw'ell of objects in fluids and more particularly to a method of and apparatus for controlling both the dwell and the depth of dwell of substantially neutrally buoyant objects such as missiles or missile capsules in water for a selected period of time.

Controlling the depth at which an object or assembly of objects will dwell has been a much desired goal in a variety of underwater programs. This goal has been achieved in the case of undersea craft through complex machinery and appendages whose operation or control is necessarily manual, however, such equipment and operation could not reasonably be applied in controlling the depth of dwell of missiles or missile capsules or the like for a variety of reasons including cost, hazard to human life, etc. Since there exists no means for satisfactorily controlling dwell and depth of dwell which is both simple in construction and requires no power source or human guidance, the present invention has resulted.

Through the present invention there is provided a device which may be attached to a missile, a missile capsule or other object whose dwell and depth of dwell is desired to be controlled, with the device including a self-contained reference pressure source linked to a gas source the release of which is controlled by the level of the lower end of an extensible tube centrally positioned in the chamber of the device. Full control is realized without any energy source or the transmission and reception of control signals from a remote station. The area of dwell is attained through a level-seeking process which entails "oscillation" or hunting between decreasing ranges of depth above and below the desired dwell area until the minimum range zone is reached. The hunting or oscillation may be terminated at the end of a preselected period of time by actuation of a mechanical or electronic timing device which arbitrarily sets the time of dwell.

Accordingly, it is an object of the present invention to provide a depth control device for controlling the dwell as well as the depth of dwell of missile capsules wherein the desired depth zone is sought by hunting" action which is controlled without the use of an electrical power supply or remote signal.

It is another object of the present invention to provide a depth control device having a self-contained pressure reference and in which the desired depth zone is sought through mechanically-controlled pro gramming of a self-contained pressure gas source.

It is a further object of the present invention to provide a buoyancy control device for use in association with neutrally buoyant objects in which the dwell and depth of dwell is self'controlled for a preselected period of time and is terminated thereafter in a sounding maneuver.

It is a still further object of this invention to provide a buoyancy control device which is adapted for attachment to neutrally buoyant objects and by means of which dwell and depth of swell are attained and maintained for selected periods of time through the cooperative action of a pressure reference and an air supply operating in response to ambient pressure and without a necessity for manual or remote control.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings in which like numerals designate like parts throughout and wherein:

FIG. 1 is a cutaway elevation view partly in section of a preferred embodiment of the buoyancy control device;

FIG. 2 is a cross section of one of the components of the buoyancy control device; and V FIG. 3 is a view showing the buoyancy control device attached to a missile capsule and maintaining the missile capsule at a desired depth and dwell.

Referring to FIG. 1, the buoyancy control device is indicated generally at 11 and includes in this embodiment an inverted open bottom container 12 having a flotation chamber 17 in which air may be trapped about a centrally disposed air release mechanism 13. A reference pressure source 14 is included to provide a reference pressure, and an air or gas supply 15 provides means for increasing buoyancy as required during operation of the device. The air release mechanism 13 controls the release of air or gas from flotation chamber 17 of the device so as to decrease buoyancy as necessary while the device is seeking the depth level represented by the reference pressure. The pressure source 14, gas supply 15 and air release mechanism 13 are interconnected to provide automatic, non-electrical control of the water level 19 within the chamber 17 which in effect controls the depth of dwell of the device 11. The reference pressure source 14 in the present embodiment includes a pair of spheres 21, only one of which is seen, the pressure within source 14 is exerted against a flexible diaphragm 22 contained in a protective sphere 23, diaphragm 22 being fastened around zone 25 of sphere 23 and connected to the release mechanism 13 via non-extensible means such as cable 28.

Gas supply 15 includes a supply source containing a sufficient supply of gas to provide for increases in buoyancy over a selected period of time. Gas supply 15 also includes pressure regulator 31 for releasing gas at a selected pressure through hose 33 into chamber 17. Pressure gauges 34 and 35 indicate, respectively, the pressure of gas remaining in source 30 and the reference pressure established in pressure source 14 as introduced therein through valve 38. Pressure regulator 31 is a demand type of regulator which continually provides a selected pressure above ambient. The regulator is used first to determine the pressure in pressure source 21 and then is set to admit gas at a desired pressure to valve 40. Gas emanating from source 30 for the purpose of increasing buoyancy is released into chamber 17 through outlet 41 of valve which, as seen in FIG. 2, is a conventional form of needle valve. The valve is shown in the closed position in FIG. 3, arm 44 when depressed pivoting about pin 45 and compressing spring 46 while needle 47 is forced downward closing passage 49. Valve 40 is attached to collar of tube 51 and moves up and down rods 6 1 with tube 51.

Release mechanism 13 includes a passage defining means such as tube 51 which may be of elastomeric material or, as shown in the present embodiment, a metallic or plastic bellows spring-engaged with the upper surface 53 of the device 11 through centrally positioned bar 54. Bar 54 extends across an opening 55 in the central area of upper surface 53 and has connected to it the upper end of a spring 58 whose lower end is connected to a collar 60 which is attached to the lower end of tube or bellows 51. The opening 55 is centrally located to minimize escape of air due to tipping of the device. Rods 61 connect the upper and lower surfaces of the device 11, 53 and 62, respectively, and guide the lower end of tube 51 vertically through sleeves 64 which are attached to collar 60. A float 67 is disposed about tube 51 and rods 61 and has attached to it a frame 68 which is disposed below the float 67. Float 67 is guided vertically by sleeves 69 which ride along rods 61 as do sleeves 64. Frame 68 is open or web-like in .form to permit substantially free flow of water therethrough and has a portion thereof disposed to contact the arm 44 which actuates valve 40. A ring 70 is attached to the end of arm 44 remote from valve 40 to permit cable 28 to be centrally positioned and be unimpeded in movement. Cable 28 is passed over pulleys 72 and 73 to provide for movement of the cable along the axes of movement of diaphragm 22 and tube 51, respectively.

Hunting or oscillation of the device is terminated through a locking mechanism 75 which includes a timer 77 connected to a squib 78 which when fired propels a cutter 79 downward and severs a cord 80 at the termination of a selected period of time. Cord 80 is spring-loaded between frame members of the device 11, the spring 81 to which it is attached providing a selected contraction so that when cord 80 is severed connector 83 will override the action of diaphragm 22 on cable 28 and pull collar 60 a selected distance downward. As shown in FIG. 3, buoyancy control device 11 is connected to the missile capsule 85 or other load by rods 88 which may be permanently attached to the device 11 and attached by removable means such as nuts, not shown, to a base plate or other end member of the missile capsule such as cap 90.

In operation, gas supply source 30 is filled to the desired pressure, and pressure reference source 21 is pressurized to the pressure representative of the depth of dwell desired for the device 11 and its attached neutrally buoyant load such as missile capsule 85. The timer 77 is set for terminating operation of the device after passage of a selected period of time. Although an electrical timer and an explosive squib have been described, it will be appreciated that cord 80 may be severed by mechanical means such as a spring-wound clock which releases a spring-loaded blade, within the scope of the invention, thereby rendering the entire operation non-electrical.

The general operation of the device will be covered first, then a more detailed description of operation. Generally, the water level 19 in chamber 17 determines whether air will be accumulated in the chamber or released therefrom. The lower end of tube 51 allows air to escape out of the container when the tube 51 is moved above the level of water in the container. The trapped air in the container continues to escape until the water level therein rises to the level of the collar 60. The tube 51 is spring loaded by spring 58 and is connected to diaphragm 22 the differential pressure against which diaphragm represents the difference between ambient water pressure and the reference pressure. When a pressure differential exists, cable 28 is moved, as is collar 60 and valve 40, permitting opening of passage 49 when arm 44 is below frame 68 of float 67 and admitting air into the container when such condition exists. Air continues to enter the chamber until arm 44 is depressed by frame 68 and closes passage 49.

When the missile capsule and attached device are lowered into the water, the two connected bodies should sink to a depth below that selected for dwell because of the inertia of the device and the fact that at atmospheric pressure diaphragm 22 will be distended downward a maximum amount thus permitting spring 58 to move collar 60 and cable 28 upward a maximum distance for the depth setting and causing a minimum of air to be trapped in container 112. With a minimum amount of air entrapped, the device will be flooded to a negative buoyancy and the connected bodies will sink to a depth greater than that represented by the reference pressure. Since missile capsule 85 is substantially neutrally buoyant, it will have greater buoyancy than the device 11 and result in the connected bodies assuming the attitude shown in FIG. 3.

Assuming the device 11 has been carried below the desired depth of dwell, the ambient water pressure on the exposed surface of diaphragm 22 will exceed the internal pressure thereon causing cable 28, valve 40 and collar 60 to be pulled downward and displacing arm 44 below frame 68. Arm 44 and piston 47 are now urged upward by the compression in spring 46 permitting escape of air through passage 49 and into the chamber 17 via outlet 41. As the air through outlet 41 fills the space in the container 12, water level 19 is forced downward until frame 68 of float 67 closes valve 40 by the weight of the float and frame on arm 44. Thus, the trapped air volume increases as the device sinks until a depth is finally reached where the device has a positive buoyancy whereupon it begins to rise. As the device rises, diaphragm 22 is forced downward by internal pressure and allows spring 58 to retract tube 51 and collar 60 upward. As collar 60 comes out of the water within the container, the trapped air escapes allowing the water level to rise inside the device thereby reducing its buoyancy. The foregoing cycle is repeated until the air or gas in supply source 30 is exhausted.

In the manner described above the device hunts a preselected depth zone and dwells within that zone as long as its air supply lasts. By using a pair of spheres 21 a relatively large volume is provided for a pressure reference source resulting in appreciably large increments of movement of diaphragm 22 in response to ambient pressure changes. These large increments provide in effect a soft spring constant and result in a smaller dwell zone amplitude. A smaller volume would result in a hard spring constant requiring greater pressure changes to effect equivalent diaphragm motion thus resulting in greater dwell zone amplitudes.

The hunting action is terminated at the end of a selected period of time by timer 77 firing squib 78 causing cord to be severed thereby releasing spring 81 which draws cable 28 and collar 60 a predetermined distance downward. Collar 60 is locked in this position permitting air to accumulate in chamber 17 in sufficient quantity to float the device.

Although a preferred embodiment has been shown and described, it will be appreciated that changes thereto may be made within the concept of the invention. Such changes could include providing pumps and an electrical power supply to operate the pumps whereby air instead of being released as the device sinks would be recompressed and used over and over again thus appreciably extending the period of dwell. Also, apparatus could be included which would admit air in step amounts into the chamber and release it in step amounts therefrom. Further, the rate of escape of air could be controlled instead of the volume of air as done in the present embodiment, and a gas producing chemical could be substituted for the pressurized gas source. Dwell could be terminating by remote signal.

It will therefore be recognized that many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

I claim:

1. A device for controlling the depth at which an object will float comprising:

a flotation chamber having a central opening in its upper surface and an open bottom;

a pressure source in said chamber;

said pressure source including a diaphragm which is exposed to the fluid in which the device is floated;

means defining a passage between the interior of said chamber and said central opening;

guide means attached to said upper surface about i said central opening;

said guide means extending transversely through said chamber;

the interior end of said passage defining means movably mounted on said guide means;

a gas supply in said chamber and means associated therewith for dispensing said gas into said chamber to provide increased buoyancy when the fluid in said chamber reaches a predetermined level; and

non-extensible means connecting the interior end of said passage defining said diaphragm;

said passage defining means defining a decreased air space in said chamber and releasing air therefrom when said device is at depths less than a predetermined depth;

said passage defining means defining means defining an increased air space in said chamber when said device is at depths greater than a predetermined depth;

said dispensing means actuable to release gas into the increased air space when the fluid in said chamber is above a predetermined level.

2. The device as defined in claim 1 wherein said means associated with said gas supply includes a float disposed about said passage defining means and a valve actuable by the float to shut off the flow of gas into said chamber when the fluid in said chamber reaches a level- 3. The device as defined in claim 2 and further including locking means connected to said non-extensible means for terminating submergence of the device;

said passage defining means including an elastomeric tube;

said locking means operating to extend said elastomeric tube to a predetermined fixed length thereby permitting sufiicient gas to collect in said chamber to cause the device to surface.

4. A device for controlling the depth at which an object will float comprising:

a regularly shaped container having a central opening in its top and an open bottom;

an expansible tube having one end attached about said central opening in sealing engagement therewith and the other end extending into said container;

guide means disposed about said central opening and extending between said top and bottom for directing movement of said expansible tube;

a collar attached to said other end of said expansible tube and slidably mounted on said guide means;

a float disposed about said tube and said guide means;

said float having a frame attached thereto which extends under said float;

spring means connecting said collar and the top of said container;

a pressure source in said container for providing a constant pressure reference;

said pressure source including a diaphragm;

non-extensible means connecting said diaphragm and said collar;

a gas supply including an outlet and connecting lines in said container for increasing buoyancy when required;

valve means in said connecting lines for controlling release of said gas;

valve actuating means mounted on said collar;

said valve actuating means including lever means actuable by said float frame when the fluid in said container is at a level determined by the pressure differential on said diaphragm;

said expansible tube defining a decreased air space in said container and releasing air therefrom when said device is at depths less than a predetermined depth;

said expansible tube defining an increased air space in said container and entrapping gas from said gas supply therein when said device is at depths greater than a predetermined depth.

5. The device as defined in claim 4 wherein said lever means includes a lever arm extending transverse to said guide means;

said lever arm having a passage for accommodating said non-extensible means axially with respect to said tube;

said valve means and said lever arm mounted on said collar for movement therewith;

said lever arm disposed below and adjacent to said float so that upon said container receiving additional gas from said gas supply said float will move downward with respect to said collar until said lever arm is actuated and the release of said gas is stopped.

6. The device as defined in claim and further including means connected to said non-extensible means for terminating submergence of the device;

a fluid comprising:

a container having openings in its bottom and a central opening in its top surface;

' collapsible tube means attached in sealing relationship at one end to said central opening;

said collapsible tube means extending into said container and terminating in a collar at its other end;

a float disposed about said tube means;

a pressure source in said container for providing a constant pressure reference;

an air supply and connecting tubing in said container for providing buoyancy when required;

guide means extending downward from the top surface of said container for directing vertical movement of said tube means;

a diaphragm in said pressure source and cable means connecting said diaphragm to the collar of said tube means; and

valve means attached to said tubing for controlling release of air;

said valve means disposed for movement along said guide means and including lever means actuable by said float to control movement of said valve means;

so that when said container is below the pressure level set by said pressure source said cable will move said collar and said valve means free of said float opening said valve and permitting air to accumulate in the upper part of said chamber so as to increase its buoyancy, and when said container is above the pressure level set by said pressure source said cable will release said collar permitting accumulated air to escape through said tube so as to decrease the buoyancy of the apparatus.

8. A method of controlling the depth at which an object will float through use of a flotation chamber comprising the steps of:

releasably attaching the chamber to the object;

pressurizing a portion of the chamber with gas upon submersion in a fluid to provide buoyancy to maintain the chamber and object substantially at a predetermined depth;

sensing the pressure differential between pressure at the predetermined depth and ambient pressure;

simultaneously decreasing the space in which the gas may be entrapped and releasing gas from the chamber when the chamber is above the predetermined depth; and

simultaneously increasing the space in which gas may be entrapped'and admitting gas into the chamber when the chamber is below the predetermined depth;

9. The method as defined in claim 8 and further innecessar to rovide buo am; at the redetermined depth and SImElIQHGOUSIY zi dmll ti p space so as to cause the chamber and object to rise to the surface.

ng gas into the greater 

1. A device for controlling the depth at which an object will float comprising: a flotation chamber having a central opening in its upper surface and an open bottom; a pressure source in said chamber; said pressure source including a diaphragm which is exposed to the fluid in which the device is floated; means defining a passage between the interior of said chamber and said central opening; guide means attached to said upper surface about said central opening; said guide means extending transversely through said chamber; the interior end of said passage defining means movably mounted on said guide means; a gas supply in said chamber and means associated therewith for dispensing said gas into said chamber to provide increased buoyancy when the fluid in said chamber reaches a predetermined level; and non-extensible means connecting the interior end of said passage defining said diaphragm; said passage defining means defining a decreased air space in said chamber and releasing air therefrom when said device is at depths less than a predetermined depth; said passage defining means defining means defining an increased air space in said chamber when said device is at depths greater than a predetermined depth; said dispensing means actuable to release gas into the increased air space when the fluid in said chamber is above a predetermined level.
 2. The device as defined in claim 1 wherein said means associated with said gas supply includes a float disposed about said passage defining means and a valve actuable by the float to shut off the flow of gas into said chamber when the fluid in said chamber reaches a level.
 3. The device as defined in claim 2 and further including locking means connected to said non-extensible means for terminating submergence of the device; said passage defining means including an elastomeric tube; said locking means operating to extend said elastomeric tube to a predetermined fixed length thereby permitting sufficient gas to collect in said chamber to cause the device to surface.
 4. A device for controlling the depth at which an object will float comprising: a regularly shaped container having a central opening in its top and an open bottom; an expansible tube having one end attached about said central opening in sealing engagement therewith and the other end extending into said container; guide means disposed about said central opening and extending between said top and bottom for directing movement of said expansible tube; a collar attached to said other end of said expansible tube and slidably mounted on said guide means; a float disposed about said tube and said guide means; said float having a frame attached thereto which extends under said float; spring means connecting said collar and the top of said container; a pressure source in said container for providing a constant pressure reference; said pressure source including a diaphragm; non-extensible means connecting said diaphragm and said collar; a gas supply including an outlet and connecting lines in said container for Increasing buoyancy when required; valve means in said connecting lines for controlling release of said gas; valve actuating means mounted on said collar; said valve actuating means including lever means actuable by said float frame when the fluid in said container is at a level determined by the pressure differential on said diaphragm; said expansible tube defining a decreased air space in said container and releasing air therefrom when said device is at depths less than a predetermined depth; said expansible tube defining an increased air space in said container and entrapping gas from said gas supply therein when said device is at depths greater than a predetermined depth.
 5. The device as defined in claim 4 wherein said lever means includes a lever arm extending transverse to said guide means; said lever arm having a passage for accommodating said non-extensible means axially with respect to said tube; said valve means and said lever arm mounted on said collar for movement therewith; said lever arm disposed below and adjacent to said float so that upon said container receiving additional gas from said gas supply said float will move downward with respect to said collar until said lever arm is actuated and the release of said gas is stopped.
 6. The device as defined in claim 5 and further including means connected to said non-extensible means for terminating submergence of the device; said last mentioned means operating to extend said expansible tube to a predetermined fixed length thereby freeing said lever arm and permitting sufficient gas to enter said chamber to cause the device to surface.
 7. Apparatus for controlling the depth of an object in a fluid comprising: a container having openings in its bottom and a central opening in its top surface; collapsible tube means attached in sealing relationship at one end to said central opening; said collapsible tube means extending into said container and terminating in a collar at its other end; a float disposed about said tube means; a pressure source in said container for providing a constant pressure reference; an air supply and connecting tubing in said container for providing buoyancy when required; guide means extending downward from the top surface of said container for directing vertical movement of said tube means; a diaphragm in said pressure source and cable means connecting said diaphragm to the collar of said tube means; and valve means attached to said tubing for controlling release of air; said valve means disposed for movement along said guide means and including lever means actuable by said float to control movement of said valve means; so that when said container is below the pressure level set by said pressure source said cable will move said collar and said valve means free of said float opening said valve and permitting air to accumulate in the upper part of said chamber so as to increase its buoyancy, and when said container is above the pressure level set by said pressure source said cable will release said collar permitting accumulated air to escape through said tube so as to decrease the buoyancy of the apparatus.
 8. A method of controlling the depth at which an object will float through use of a flotation chamber comprising the steps of: releasably attaching the chamber to the object; pressurizing a portion of the chamber with gas upon submersion in a fluid to provide buoyancy to maintain the chamber and object substantially at a predetermined depth; sensing the pressure differential between pressure at the predetermined depth and ambient pressure; simultaneously decreasing the space in which the gas may be entrapped and releasing gas from the chamber when the chamber is above the predetermined depth; and simultaneously increasing the space in which gas may be entrapped and admitting gas into the chamber when the chamber is below the predetermined depth.
 9. The method as defined in claim 8 and further including the step of maintaining a greater space in the chamber in which gas may be entrapped than that necessary to provide buoyancy at the predetermined depth and simultaneously admitting gas into the greater space so as to cause the chamber and object to rise to the surface. 